The present invention relates to saw blades of the kind used for sawing hard and/or abrasive materials such as, for example, granite, marble, concrete, asphalt, and the like; and more particularly to metal-clad abrasive particle pellets useful in forming saw blade cutting segments.
Conventionally, the cutting of hard materials such as, for example, granite, marble, filled concrete, asphalt, and the like, has been achieved using diamond saws. The blade of saws of this type comprises a circular steel disk having a plurality of spaced segments about its cutting edge, which segments consist essentially of diamond abrasive bonded in a suitable alloy or metal matrix, such as bronze or cobalt, for example. The diamond abrasive typically is either a single crystal natural diamond or a single crystal synthetic diamond. U.S. Pat. No. 4,883,500 proposes the use of a combination of thermally stable polycrystalline diamond cutting elements and single crystal diamond cutting elements dispersed in a bonding matrix.
A variety of problems have plagued the artisan in fabricating segments and saw blades containing such segments. For example, to optimize diamond saw blade performance, it would be desirable to prevent agglomeration of diamond in the metal bond powders during mixing and blending. This would permit maximum utilization of the diamond abrasive crystals. Further, it would be convenient to have controlled porosity within each segment to provide localized coolant during use, to minimize thermal degradation of diamond, and/or the bond metal.
In granite sawing with rotary saw blades, for example, lateral deflection of the blade as it enters harder areas of the stone can give rise to non-flat portions of the surface being cut. This leads to the need for expensive grinding and reduces the profit for the stone processor. One solution to this problem in the field has been to make sandwich segments with differential wear patterns to provide a matching track on the stone which reduces the chances of lateral blade deflection during the cut. Until now, the differential wear has been achieved by either varying concentration of the diamond across the face, or by adding wear resistant material in the outer portions of the segments, such as proposed in U.S. Pat. No. 4,883,500, cited above. These methods use the technique for filling the pressing cavity in three consecutive cold pressing steps, and then hot pressing to sinter the metal matrix powder in a separate operation.
It has been common practice for several decades to blend or mix diamond abrasive powders with fine metal powders to form segments by hot pressing in a sintering press. Air-borne fine metal powders, if toxic or carcinogenic, represent a potential health hazard. In addition, differences in size, shape, and density between diamond and metals make production of homogeneous mixtures difficult. Also, it would be convenient to be able to automate mold loading.